Irma Stern's Watussi Dancers is valued at £800,000-1.2m ($1m-1.5m) ahead of a sale at Bonhams London.

Stern experienced the famous Watussi dancers of Rwanda on her 1942 tour of Africa.

Irma Stern observed the Watussi dancers in 1942

She describes the spectacle in her journal: "A Watussi runs in, yelling and beating the ground with his stick, followed by twenty to thirty men, all yelling.

"The first group of dancers enters the arena, unbelievably tall and slender men, like reeds, their well-moulded young bodies garlanded with brilliant ropes of beads, swaying in a strange rhythm, and at the same time swinging long sticks…

"Their whirling yellow loin-cloths are decorated with geometrical patterns: red suns, black moons, and arrow heads, the symbol of birds in flight.

"The rhythm of the dance grows faster and faster, until it ends in a frenzy. The musicians then enter crouching low…"

The painting expertly captures the frenetic energy of the moment.

Stern is South Africa's most celebrated painter.

Her work has proven hugely popular among collectors of late, with a record £3m ($4.6m) paid for her Arab Priest at Bonhams in 2011.

More recently, a Stern painting sold to raise funds for Nelson Mandela's legal fees in the 1980s made £842,500 ($1.2m) at Bonhams last year.

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